The thing with top dressing is, it's only part of the story. You need microbial life, to break down those dry amendments.
Since you were feeding synthetic nutes, you weren't giving the microbes much to eat.
If it were me, I'd top dress the amendments with earth worm castings, and water in a compost Tea.
Also I'd add mulch. There's 2 reasons for the mulch.
1. A place for the microbes at the top of the soil, out of light.
2. Helps retain moisture at the top of soil, where the dry amendments are breaking down.
Also, container size/volume, matters. A big enough plant, in too small of a container, will consume all the nutrition, faster than microbes can break down the organic matter.
Having a bottle of organic nutes, like neptune's harvest (or something similar), is good to have on hand, just in case.